Stamp having an antisticking layer and a method of forming of repairing such a stamp

ABSTRACT

A stamp for use in transferring a pattern in nano-scale has a monomolecular antisticking layer. The anti-sticking layer comprises molecular chains, which are covalently bound to the surface of the stamp and which each comprise at least one fluorine-containing group. Each molecular chain contains a group Q, which comprises a bond which is weaker than the other bonds in the molecular chain as well as the covalent bond that binds the molecular chain to the surface of the stamp. Splitting of said bond in the group Q creates a group Q1, which is attached to the part of the molecular chain being left on the surface of the stamp and which is capable of reacting with a fluorine-containing compound to restore the antisticking layer. In a method of manufacturing a stamp for use in transferring a pattern in nanoscale, the stamp is provided with the above-mentioned molecular chain. In a method of repairing a damaged antisticking layer of the above-mentioned stamp, the stamp is treated with a repairing reagent, which has a coupling end, which is capable of reacting with the group Q1, and a fluorine-containing group located at the other end of the repairing reagent.

FIELD OF THE INVENTION

The present invention relates to a stamp for use in transferring apattern in nanoscale, which stamp has a monomolecular antistickinglayer.

The invention also relates to a method of manufacturing a stamp for usein transferring a pattern in nanoscale, which stamp has a monomolecularantisticking layer.

The invention further relates to a method of repairing saidmonomolecular antisticking layer.

BACKGROUND ART

In the replication of nanostructures, use is often made of a stamp,which hot embosses a pattern into a plate coated with a suitablepolymer, such as a thermoplastic. It is necessary to provide anantisticking boundary surface between the patterned stamp and thepolymer to prevent thermoplastic from getting stuck to and contaminatingthe surface of the stamp when the stamp is released from the coatedplate after embossing. Also the pattern replicated on the plate can bedamaged by such sticking. For successful embossing, the stamp must thusbe chemically and mechanically stable and have a low tendency to stickto polymers.

In Microelectronic Engineering 35 (1997) 381-384, R. W. Jaszewski et al.disclose that the surface of the stamp can be covered with anultra-thin, antisticking layer of PTFE. The layer is precipitated bymeans of plasma polymerisation or ion sputtering from a plasma.According to Jaszewski et al., the quality of the film deteriorates inthe embossing. Obviously, the film is not sufficiently stable.

SUMMARY OF THE INVENTION

According to the present invention, the above drawbacks are obviated orreduced and a stamp with an antisticking layer is obtained, which isstable, has good antisticking properties and can easily be repaired whendamaged or worn.

More specifically, the invention provides a stamp for use intransferring a pattern in nanoscale, which stamp has a monomolecularantisticking layer and is characterised in that said antisticking layercomprises molecular chains, which are covalently bound to the surface ofthe stamp and which each comprise at least one fluorine-containinggroup, each molecular chain containing a group Q, which comprises a bondwhich is weaker than the other bonds in the molecular chain as well asthe covalent bond that binds the molecular chain to the surface of thestamp, splitting of said bond in the group Q creating a group Q1, whichis attached to the part of the molecular chain being left on the surfaceof the stamp and which is capable of reacting with a fluorine-containingcompound to restore the antisticking layer.

The invention further relates to a method of manufacturing a stamp foruse in transferring a pattern in nanoscale, which stamp has amonomolecular antisticking layer, said method being characterised inthat the surface of the stamp is provided with molecular chains, whichare covalently bound to the surface of the stamp and which each compriseat least one fluorine-containing group and a group Q, which comprises abond which is weaker than the other bonds in the molecular chain as wellas the covalent bond that binds the molecular chain to the surface ofthe stamp, splitting of said bond in the group Q creating a group Q1,which is attached to the part of the molecular chain being left on thesurface of the stamp and which is capable of reacting with afluorine-containing compound to restore the antisticking layer.

The invention also relates to a method of repairing a damagedmonomolecular antisticking layer on a stamp as stated above, whichmethod is characterised in

-   -   that the stamp is treated with a repairing reagent, which has a        coupling end, which is capable of reacting with the group Q1,        and a fluorine-containing group located at the other end of the        repairing reagent,    -   that the coupling end of the repairing reagent is bound to the        group Q1 which is attached to the surface of the stamp, the        group Q being formed anew.

Further advantages and features of the invention will be apparent fromthe description below and the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

A non-limiting example of transferring a pattern in nanoscale isnanoembossing lithography or nanoimprint lithography, which is atechnique for mass-production of nanostructures. A stamp is providedwith a nanopattern on its surface. The stamp is heated and pressedagainst a substrate which is coated with a polymer layer, whereby thepattern is transferred to the polymer layer. Nano-imprinting isdescribed in more detail in U.S. Pat. No. 5,772,905 and U.S. Pat. No.5,259,926. The stamp according to the present invention can also be usedin other embossing processes.

The expression “nanoscale” is not to be understood as only relating tostructures within the range of sub-micrometers, that is, structureshaving a size within the range of 1-1000 nm. A stamp often has a patternwith structures within-the range of submicrometers-as well as structureswith a size of up to 100 micrometers and more, for instance up to about5 mm. The present invention is preferably applicable to stampscomprising structures within the range of submicrometers and/or withinthe range of 1-100 micrometers. The best effect of the invention isachieved with structures within the range of submicrometers since suchstructures are relatively more sensitive to sticking when releasing thestamp.

The present invention is based on the discovery that a stableantisticking layer can be provided on the surface of the stamp byattaching molecular chains to the stamp which have antistickingproperties. The molecular chains are formed in such a manner that theantisticking properties can easily be recreated when the antistickinglayer is worn after being used for some time.

The surface of the stamp is conveniently made of a material M which issuitable for producing nanostructured patterns. Examples of suchmaterials M are Si, Al, Ti, Ni, Cr and oxides thereof. Si isparticularly suitable since it has satisfactory hardness and is easy towork when forming patterns in nanoscale. If the surface is made ofmetal, such as Al, Ti, Cr, Ni, it is normally preferable for the surfaceto have an oxide layer. To obtain a stronger oxide layer, the surfacecan be oxidised, for instance by means of an oxygen plasma. In somemetals, such as Ni, Cr, it is particularly suitable to generate such astronger oxide layer.

According to a preferred embodiment of the invention, a first and asecond reagent are used. The first reagent is bound in a first reactionto the surface of the stamp, whereas the second reagent is bound in asecond reaction to the first reagent. The reason why this embodiment ispreferred is that it is relatively easy to obtain commercially availablecompounds which can suitably be used as first and second reagents.

A first reagent to be used in manufacturing the stamp according to theinvention has at least two functional groups. A first functional groupis intended to bind to the surface of the stamp. One example of such afirst functional group is a silane group with the formula(B0)_(3-n)R′_(n)Si—. The silane group can be bound to the surface of thestamp by means of a group B1 on the surface of the stamp, which can beM- or M-O—, where O is oxygen. In the present application, “silanegroup” also relates to the above group after this group has been boundto the stamp. The silane group can comprise n aliphatic groups R′ and3-n reactive binding groups B0, where n=0, 1 or 2. B0 is suitably ahydrolysable group. Suitable reactive binding groups B0 are chlorine(Cl) or alkoxy groups, preferably C₁₋₄ alkoxy groups, more preferablyC₁₋₂ alkoxy groups, such as ethoxy groups (EtO), methoxy groups (MeO).The aliphatic groups R′ are suitably, if they are at all present, shortsaturated aliphatic groups, preferably C₁₋₄ alkyl groups, morepreferably C₁₋₂ alkyl groups such as ethyl groups and methyl groups.When n=1 or 2 and R′ is a methyl group, a smaller binding surface isobtained, that is, the monomolecular layer can be packed tighter. Thestrongest bond to the surface is, however, obtained when n=0, that is,when the silane group has three reactive binding groups B0. Thus, oneexample of a suitable first functional group is:

The second functional group X1 of the first reagent is suitably selectedso as not to react or so as to react only to a limited extent with thesurface of the stamp. Such a functional group has the advantage that ahomogeneous monomolecular layer with a well-defined end group isprovided when treating the surface of the stamp with the first reagent.Thus, the group X1 is suitably a nonhydrolysable group. The group X1should not either react with the first functional group. Suitable groupsX1 are, for instance, —SH, —NH₂ and —OH. When X1 is an —NH₂ group, B0must not be chlorine, since this would result in undesirablepolymerisation reactions.

The first and second functional groups of the first reagent are suitablyattached at two opposed ends of a carbon compound R1. Preferably, such acarbon compound R1 is a carbon chain, which is unbranched or has shortbranches which suitably have a length of 1-6 carbon atoms, morepreferably 1-3 carbon atoms. The carbon chain is suitably a saturated,aliphatic carbon chain. Unsaturated carbon chains can participate inundesirable side reactions and highly branched or cyclic compounds takeup unnecessary room at the surface of the stamp, which reduces thedensity of the antisticking functionality on this surface.

The second functional group X1 can affect the electron density in theclosest atoms in the molecule, which may result in undesirable effectson the first functional group. Therefore, it is suitable that the R1group should have a structure that “isolates”, in terms of electrondensity, the group X1 from the first functional group. In aliphatic,saturated carbon chains, the CH₂ group which is situated closest to X1is highly affected, the next CH₂ group is somewhat affected, whereas thethird CH₂ group is substantially unaffected by X1. The group R1 issuitably unsubstituted so as not to affect negatively the first andsecond functional groups. Very long carbon chains increase the risk of abreak on the chain and make the antisticking layer less stable, as thecarbon chains can change their angle to the surface. Thus, R1 suitablyhas a length, from the first to the second functional group, of 1-10carbon atoms, preferably 2-5 carbon atoms and most preferably 3 carbonatoms. The group R1 can also be provided with shorter branches, suitablyof a length of 1-4 carbon atoms, preferably 1-2 carbon atoms, forinstance, with a view to increasing the antisticking functionality or toenhancing the bond to the surface:

When in the last-mentioned example X1 is —SH, a sulphur bridge S—Susually forms. The sulphur bridge will react in the same way as twoseparate —SH groups and is therefore equivalent to these groups.

It is suitable to select a first reagent which fulfils the criteriadescribed above and which is available on the market. Examples ofpreferred first reagents are thus mercaptopropyltriethoxysilane:

and aminopropyltriethoxysilane:

The second reagent comprises a first part X2, which is intended to bebound to the X1 group of the first reagent, and a second part R2, whichhas an antisticking functionality.

The group X2 is selected so as to be suitable for reaction with the X1group in the first reagent. The reaction should result in a bond whichis sufficiently strong to maintain the antisticking functionality at thesurface of the stamp. The bond which forms between X1 and X2 is,however, weaker than the other bonds in the monomolecular layer. Anybreak on the molecular chain will thus occur in a predictable position,namely between X1 and X2. Examples of suitable combinations of X1 and X2are: X1=—SH group and X2=—SH group, which can form a sulphur bridge,X1=—NH₂ group and X2=Cl—(C═O)—, which can form a peptide bond, andX1=—OH and X2=HO—(C═O)—, which can form an ester. It is particularlypreferable that X1 as well as X2 should be —SH groups, since they form abond which is strong enough to maintain the antisticking functionality,but is weaker than, for instance, bonds between carbon atoms in themolecular chain, between carbon atoms and sulphur atoms and between asilane group and the surface of the stamp.

The group R2 suitably contains fluorine atoms, which yield the desirableantisticking functionality. It is particularly suitable that R2 shouldhave a free end group, which contains a carbon atom to which one or morefluorine atoms are bound. Preferably the group R2 is a fluorinated,aliphatic, saturated carbon chain. Unsaturated carbon chains canparticipate in undesirable side reactions and highly branched or cycliccompounds take up too much space, which reduces the density of theantisticking functionality.

The fluorine atoms will affect the electron density in the closest atomsin the molecule, which may result in undesirable effects on the bondbetween X2 and X1. Therefore, it is suitable that the group R2 shouldhave a structure that “isolates”, in terms of electron density, the X2group from the fluorine atoms. In aliphatic, saturated carbon chains,the CH₂ group closest to a carbon atom, which is substituted withfluorine, is highly affected, whereas the next CH₂ group is almostunaffected. The group R2 suitably has at least 1 and preferably 2 CH₂groups in a row closest to the group X2. In longer chains of CH₂ groups,there is an increasing risk of breakage. Thus, the number of CH₂ groupsin a row should not exceed 5.

R2 suitably has at least one perfluorinated carbon atom. Preferably thiscarbon atom is the end group of the R2 group, that is a CF₃ group. Moreperfluorinated carbon atoms result in better antisticking functionality.Very long carbon chains increase the risk of a break on the chain andmake the antisticking layer less stable, as the carbon chains can changetheir angle to the surface. Thus, R2 suitably has 1-12 perfluorinatedcarbon atoms, preferably 2-8 perfluorinated carbon atoms and mostpreferably 3-6 perfluorinated carbon atoms. The group R2 can also beprovided with shorter branches, suitably of a length of 1-6 carbonatoms, more preferably 1-3 carbon atoms, for instance with a view toincreasing the antisticking functionality or to enhancing the bond byattaching to two groups X1.

The last-mentioned variant, which is branched at the end of the group R2that is situated furthest away from the group X2, has a larger “head”.The nanostructured pattern on the surface of the stamp is like alandscape with crests and valleys. It may sometimes be difficult toprovide a sufficiently high density of the antisticking functionality atthe crests. An R2 group which is branched and has two or more CF₃ groupsat the end that is not intended to bind to the first reagent fills outthe space better, thereby improving the antisticking functionality atthe crests, sharp corners and other structures on the surface of thestamp.

It is suitable to select a second reagent, which fulfils the criteriadescribed above and which is available on the market. Examples ofpreferred second reagents are thus 1H, 1H, 2H, 2H-perfluorooctanethiol:SH—(CH₂)₂—(CF₂)₅—CF₃and fluorinated organic acid chlorides, such as 2H, 2H, 3H,3H-perfluorohexaneacidchloride:Cl—(C═O)—(CH₂)₂—(CF₂)₂—CF₃

According to a less preferred embodiment of the invention, one singlereagent is used. This single reagent is bound in a reaction to thesurface of the stamp. The reason why this embodiment is less preferredis that there are few commercially available compounds which, in one andthe same compound, comprise suitable functional groups which can bind tothe surface of the stamp, groups which have antisticking properties andin addition Q groups, which comprise a weaker bond. The single reagentused in this less preferred embodiment suitably has properties involvingthe above groups and being similar to the properties described aboveconcerning the first and second reagents, with the exception that theabove groups X1 and X2 are replaced by a group Q. Thus, this singlereagent can, for instance, have the formula (B0)_(3-n)R′_(n)SiR1QR2,where the respective groups suitably have the properties and limitationsdescribed above. An example of a suitable single reagent in this lesspreferred embodiment is:

In a preferred method of manufacturing a stamp according to theinvention, the nanostructured pattern is first formed on the surface ofthe stamp. This patterning can be effected, for instance, by etching orin some other prior-art manner. The surface which, for instance, can bea silicon surface, is subsequently cleaned by means of, for instance,1-4 organic solvents, such as trichloroethylene, ethanol, acetone andisopropanol, in succession. The last solvent is suitably isopropanol,which is particularly suitable to ensure that the surface is free fromwater. In some cases, it is necessary to etch away the oxide layer ofthe surface, for instance, with fluoro-hydrogen acid, HF, (10-40%solution) to provide a homogeneous surface layer. The stamp is thentreated with the first reagent. The first treatment can be performed ineither liquid phase or in gaseous phase.

In a first treatment in liquid phase, the stamp is placed for about 1-5h in a vessel containing about 0.1-1% of the first reagent in an organicsolvent, suitably an alkane, at room temperature. The stamp is thenwashed, suitably by means of a series of 1-4 organic solvents similar tothose mentioned above to remove the compounds which have not beencovalently bound to the surface.

In a first treatment in gaseous phase, the stamp is placed in an ovenwith nitrogen gas atmosphere at a temperature of about 50-250° C.,suitably about 150-220° C., and at a pressure at which the first reagentis in gaseous phase, usually a pressure of about 0.5-20 kPa, suitablyabout 1-3 kPa. The exact combination of temperature and pressure isselected in such a manner that the current first reagent is certain tobe in gaseous phase. The first reagent is subsequently injected into theoven, vaporised and allowed to react with the stamp for about 0.5-10 h.Then the stamp is removed from the oven and allowed to cool, whereuponit is washed with a series of organic solvents as described above.

The gaseous phase reaction is much more complicated to perform than thecomparatively easy liquid phase reaction. Nevertheless, the gaseousphase reaction often yields a much more homogeneous monolayer on thesurface of the stamp and is thus preferable in many cases.

Thus, in a silicon stamp and using the preferred first reagentsmentioned above, the following results can be obtained after the firsttreatment:

Depending on the original structure of the surface, the actual structureof the bond between the silicon surface and the silane group as well asthe residual product, that is ethane or ethanol in the example above,can be somewhat affected. It is assumed, although not demonstrated, thatthe outermost layer of the surface can have, for instance, thecomposition Si, SiH, SiOH or SiO depending on how the surface has beentreated. The bond between the silicon surface and the silane group isassumed to have the structure (Si)₃Si or (Si—O)₃Si, but the exactstructure is not completely clear. The above formulas are thus intendedto designate a silane group which is bound to a silicon surface,irrespective of the exact structure of the actual bond.

After that, the washed stamp is treated with the second reagent. Thissecond treatment can be effected both in liquid phase and in gaseousphase.

In a second treatment in liquid phase, the stamp is placed in a vesselcontaining a suitable solvent, for instance an alkane, with about 1-10%of the second reagent at room temperature. The reaction is allowed tocontinue for about 6-24 h, whereupon the stamp is taken out and cleanedby dipping into one or more baths with a suitable, organic solvent, forinstance alkane as above. The stamp is then dried and ready for use innanoimprinting.

In a second treatment in gaseous phase, the stamp is placed in an ovenwith nitrogen gas atmosphere at a temperature of about 50-200° C.,preferably about 70-120° C. The oven is evacuated to a low pressure,suitably about 1-20 kPa, more preferably about 5-10 kPa. The exactcombination of temperature and pressure is selected in such a mannerthat the current second reagent is certain to be in gaseous phase. Thesecond reagent is injected into the oven, vaporised and allowed to reactfor about 1-10 h with the monolayer on the surface of the stamp. Thestamp is removed from the oven, allowed to cool, then cleaned in theabove-described manner and is subsequently ready for use innanoimprinting.

In the second treatment, the surface of the stamp is already from thebeginning covered with a monomolecular layer. Consequently, a reactionin gaseous phase is usually not advantageous to the homogeneity of thelayer. The reaction in liquid phase is much more easy to perform andnormally preferable in the second treatment. However, in case of verysmall nanostructures a reaction in gaseous phase is sometimes necessaryto obtain a sufficiently even layer after the reaction.

The groups X1 of the first reagent can sometimes be bound to each other.One example is groups X1 in the form of —SH groups which can formsulphur bridges, S—S, both within one and the same molecule and betweenseveral molecules. Therefore, the second reagent should be added inlarge excess, since such an excess tends to break any internal bondsbetween the groups X1 of the first reagent.

Thus, in a reaction between the above-described product after the firsttreatment and the above-described preferred second reagents, thefollowing results can be obtained after the second treatment when thegroups X1 and X2 have reacted and formed a group Q in the form of S—Sand NH—C═O, respectively:

According to a less preferred embodiment, an antisticking layer isformed by attaching directly a ready-made molecular chain to the surfaceof the stamp, for instance a molecular chain comprising a group whichcan bind to the surface of the stamp, a Q group and at least onefluorine-containing group. However, such a ready-made molecular chain,which can for instance be in the form of the above-described singlereagent, is usually expensive and difficult to obtain, which makes theabove-described preferred method comprising a first and a secondtreatment in succession usually preferable to a direct attachment in onestep of a ready-made molecular chain. Attachment of a ready-mademolecular chain, in one single step according to the last-mentioned,less preferred embodiment, is performed substantially in the same mannerand under the same conditions as described above in connection with thefirst treatment.

A ready-made group Q can also be included in the first or the secondreagent already from the beginning. In such a case, the group Q is thusnot formed of X1 and X2.

When a stamp has been used for many nanoimprinting operations, itsantisticking layer may be damaged. Such damage can arise when parts ofthe monomolecular layer get stuck to the polymer layer during embossingor the layer can be damaged when the stamp is released from the polymerlayer after embossing or when the stamp is being cleaned. It is normallyvery expensive to discard such a damaged stamp and manufacture a newone.

According to a preferred embodiment of the invention, the group Q isselected so that a bond in the group Q is somewhat weaker than the otherbonds in the molecular chain as well as the covalent bond which attachesthe molecular chain to the surface of the stamp. The weaker bond in thegroup Q will thus break first when the molecular chain is exposed tostrain, for instance, tensile or bending stress. A damaged antistickinglayer will then be deprived of its antisticking functionality butnormally have an intact monomolecular layer comprising short molecularchains with a well defined end group Q1 which has formed when the groupQ was split. Such a damaged layer can have the following structure:

The end group Q1 shown above in the form of an internal sulphur bridgecan instead be separate groups Q1 bound to the respective CH₂ groups inthe form of —SH groups depending on the conditions prevailing at theoccurrence of the damage and how the stamp has been treated since then.The damaged antisticking layer can easily be repaired, therebyrecovering its original antisticking functionality in the following way.First, the stamp is washed with some suitable organic solvent, forinstance an alkane. The stamp is then placed in a vessel which containsa suitable solvent, for instance an alkane, with about 1-10% of arepairing reagent at room temperature. The reaction is allowed toproceed for about 6-24 h, whereupon the stamp is taken up and cleaned bydipping into one or more baths with a suitable, organic solvent, forinstance the above alkane. The stamp, which after the repair treatmenthas an antisticking layer of substantially the same quality as when thestamp was new, is subsequently dried and is then ready to be used againin nanoimprinting.

The repairing reagent will normally be the same compound as the secondreagent which was used when the original antisticking layer wasmanufactured since such a repairing reagent normally yields the mosteven surface. It is, however, also possible to use a repairing reagentthat fulfils the above criteria for a second reagent, but that is notexactly identical to the second reagent which is used in the manufactureof the stamp. One example of the latter is that it can, under someconditions, be of interest during repair to attach a somewhat longer ormore branched molecular chain. The reason for this is that the wear onthe antisticking layer is usually most important at the angles andsimilar structures where the surface coverage of the molecular chains isat its minimum. By binding a longer and/or more branched chain to theseworn positions when repairing, a thicker more resistant layer isobtained in exactly the positions of maximum wear.

If the stamp has originally been treated with a ready-made molecularchain or a first or second reagent which contained a ready-made group Q,the repairing reagent is suitably selected so as to resemble the “tail”which came off the molecular chain when the group Q was split.

The repair treatment can also be carried out in gaseous phase. Atreatment in gaseous phase is not as easy as a liquid phase treatment,and since the quality of the repaired antisticking layer is oftensubstantially the same, the liquid phase reaction is usually preferred.However, in case of very small nanostructures, that is structures of asize of less than about 100 nm, the reaction sometimes has to take placein gaseous phase in order to obtain a sufficiently even layer after therepair.

The repairing reagent should be added in large excess since this, forinstance, makes the above-described internal sulphur bridges break,whereby the monomolecular layer on the surface of the stamp binds therepairing reagent instead. After the repair, the surface of the stampwill thus have, for instance, the following structure:

Therefore, one advantage of the present invention is that two relativelysimple and cheap compounds, in the form of the first and the secondreagent, can be used to form a stable antisticking layer withsatisfactory chemical and mechanical properties. By using a group Q, theantisticking layer can be restored when damaged or worn. In aparticularly preferred embodiment, in which the bond Q is weaker thanthe other bonds in the molecular chain, a well-defined fracture surfaceis obtained in case of damage, which surface does not have a detrimentaleffect on the ordered monomolecular structure. Then the antistickinglayer can easily be repaired by the addition of a repairing reagent.

The expression “weaker” is used above for a bond, which unites amolecular chain and is included in the group Q, in the sense that saidbond is weaker than the other bonds in the molecular chain as well asthe bond that attaches the molecular chain to the surface of the stampunder the conditions (such as temperature, pressure, etc) prevailing inthe nanoimprinting process. The expression “weaker” in connection withsaid bond is, however, to be interpreted in a wider sense. It is, forinstance, possible to select a group Q which has a bond that is weakerunder specific conditions. For instance, a stamp with a wornantisticking layer can, in connection with a repairing process, first besubject to conditions such that substantially all the groups Q aresplit, whereby a monomolecular layer is obtained in which each molecularchain has a group Q1 as end group. This layer can then be repaired bythe addition of a repairing reagent according to that stated above. Oneadvantage of exposing the stamp to conditions under which all the groupsQ are split is that also molecular chains, which have been damaged inthe embossing without the group Q being split, for instance molecularchains in which only the actual fluorine-containing group has beendamaged, can be repaired. It will also be possible to repair damagewhich has occurred close to the surface of the stamp, since it will beeasier for new molecules, which are intended to bind directly to thesurface of the stamp, to reach the surface when the groups Q have beensplit and a “tail” has been removed from each molecular chain.

Examples of Q groups which are weaker under some conditions are estersand thioesters. In the former case, the surface of the stamp can firstbe provided with a first reagent in the form of an alcohol, forinstance:

The first reagent is attached to the surface of the stamp, whereupon thestamp is treated with a second reagent in the form of a carboxylic acid,which for instance results in the following compound on the surface ofthe stamp by esterification:

It is also possible to use a first reagent with an —SH group, in whichcase a thioester is formed, for instance:

Naturally, it is also possible to first attach a first reagent with acarboxylic acid group to the surface of the stamp and then allow thiscarboxylic acid group to react with a second reagent in the form of athiol or an alcohol. As the carboxyl acid group, under some conditions,can react with the surface of the stamp, this is less preferable.

The above ester bonds and thioester bonds are very strong bonds, whichcan be broken by dipping the stamp into a beaker which contains aliquid, such as a hydrochloric acid solution, with a low pH, forinstance pH 0-2, which results in an acid ester hydrolysis, or a liquid,such as a sodium hydroxide solution, with a high pH, for instance pH10-13, which results in an alkaline ester hydrolysis. In both cases, agroup Q1 forms on the part of the respective molecular chains that isleft on the surface of the stamp, which group Q1, after washing of thestamp, can react with a repairing reagent to restore the antistickinglayer of the stamp.

Another example of the conditions under which a bond in the Q group isweaker is when affected by an enzyme. In this case, the stamp is dippedinto a beaker which contains an aqueous solution with a suitable enzyme.The enzyme breaks bonds in Q groups and forms Q1 groups on the part ofthe respective molecular chains that is left on the surface of thestamp. After the enzyme treatment, the stamp is washed and can berepaired as described above. Examples of bonds that are weaker under theinfluence of a suitable enzyme are peptide bonds, which can be split bypeptidases, for instance endopeptidases, such as pepsin, trypsin,papain, as well as ester bonds and thioester bonds, which can be splitby peptidases, for instance carboxy peptidases, such as carboxypeptidase A.

It is also conceivable to etch away the entire molecule layer, forinstance, by etching with hydrofluoric acid, HF, which attacks thesurface layer of the stamp, such as silicon dioxide groups in case of asilicon surface, and subsequently attach a completely new molecule layerto the stamp according to one of the above-mentioned methods.

EXAMPLE 1

A stamp made of silicon was etched to form a nanostructured pattern. Thestamp was washed with, in succession, trichloroethylene, ethanol andisopropanol. The stamp was subsequently dipped into a beaker with hexaneat room temperature with 0.2% mercaptopropyltriethoxysilane, whichcorresponded to an excess amount of mercaptopropyltriethoxysilane, andwas allowed to react for 4 h. The stamp was then removed from the beakerand cleaned with, in succession, trichloroethylene, ethanol andisopropanol. The stamp was dried and subsequently placed in a beaker,which contained hexane at room temperature with 2% 1H, 1H, 2H,2H-perfluorooctanethiol. After 16 h, the stamp was removed from thevessel, washed with hexane in three successive baths and then dried. Thestamp was tested in a nanoimprint lithography process and was found toresist 50 embossings without any particular signs of wear beingdetected.

EXAMPLE 2

A stamp made of silicon was patterned and washed in the manner describedin Example 1. The stamp was subsequently placed in an oven, which had atemperature of 200° C. and was evacuated to a pressure of 1 kPa.Mercaptopropyltriethoxysilane was injected in large excess into the ovenand vaporised. The stamp was allowed to react with themercaptopropyltriethoxysilane for 3 h and was then removed from the ovenand allowed to cool. The stamp was cleaned and treated with 1H, 1H, 2H.2H-perfluorooctanethiol in liquid phase in the manner described inExample 1. The stamp was tested in a nanoimprint lithography process andwas found to resist 50 embossings without any particular signs of wearbeing detected.

EXAMPLE 3

The experiment in Example 2 was repeated with materials and reagentsaccording to Table 1: TABLE 1 Combinations of materials and compoundsused in Example 3. Surface of the stamp First reagent Second reagent Si(MeO)₃Si(CH₂)₃NH₂ Cl(C═O)(CH₂)₂C(CF₃)₃ Si Cl₃Si(CH₂)₃SHSH(CH₂)₂(CF₂)₇CF₃ Si (EtO)₃Si(CH₂)₃OH HO(C═O)(CH₂)₂(CF₂)₂CF₃ Al(MeO)₃Si(CH₂)₃SH SH(CH₂)₂(CF₂)₅CF₃ Al Cl₃Si(CH₂)₃SH SH(CH₂)₂(CF₂)₂CF₃Ni* (EtO)₃Si(CH₂)₃SH SH(CH₂)₂(CF₂)₅CF₃ Ti (EtO)₃Si(CH₂)₃SHSH(CH₂)₂(CF₂)₅CF₃*The surface of Ni was first treated with an oxygen plasma to oxidisethe surface.

The finished stamps were tested in a nanoimprint lithography process andall of them were found to resist 50 embossings without any particularsigns of wear being detected.

EXAMPLE 4

A stamp manufactured according to Example 2, after several hundredembossings, started to show signs of sticking to the polymer layer whenthe stamp was to be removed after embossing. The sticking was detectedby examining the surface of the stamp in an optical microscope, whichshowed that residues of the polymer layer were stuck to the surface ofthe stamp. The stamp was cleaned by being dipped into three successivebaths with hexane. The stamp was then placed in a beaker which containedhexane at room temperature with 2% of 1H_(,) 1H, 2H,2H-perfluorooctanethiol, which was present in large excess. After 16 h,the stamp was removed from the vessel, cleaned with hexane in threesuccessive baths and then dried. The repaired stamp was tested in ananoimprint lithography process and was found to resist 50 embossingswithout any particular signs of wear being detected. The antistickingfunctionality of the repaired stamp was, as far as could be judged,equal to that of a new stamp.

1. A stamp for use in transferring a pattern in nanoscale, which stamphas a monomolecular antisticking layer, characterised in that saidantisticking layer comprises molecular chains, which are covalentlybound to the surface of the stamp and which each comprise at least onefluorine-containing group, each molecular chain containing a group Q,which comprises a bond which is weaker than the other bonds in themolecular chain as well as the covalent bond that binds the molecularchain to the surface of the stamp, splitting of said bond in the group Qcreating a group Q1, which is attached to the part of the molecularchain being left on the surface of the stamp and which is capable ofreacting with a fluorine-containing compound to restore the antistickinglayer.
 2. A stamp as claimed in claim 1, in which the antisticking layercomprises a silane group.
 3. A stamp as claimed in claim 2, in which thesurface of the stamp is made of a material M, which is selected fromsilicon, aluminium, nickel, chromium and titanium or oxides thereof, thesilane group of the antisticking layer being bound to the surface bymeans of at least one group B1, which is selected from M- and M-O—.
 4. Astamp as claimed in claim 3, in which the antisticking layer has a firstpart, which has the general formula (B1)_(3-n)R′_(n)SiR1X1, where n is0, 1 or 2, R′ is an aliphatic, saturated carbon compound, Si is thesilane group, R1 is a carbon chain and where X1 is a first couplinggroup, and a second part, which has the general formula X2R2, where X2is a second coupling group which is bound to X1 and which together withX1 forms the group Q and where R2 is a fluorine-containing hydrocarboncompound.
 5. A stamp as claimed in claim 4, in which R1 is a carbonchain which has a length from the silane group to X1 of 2-10 carbonatoms and preferably is saturated and unsubstituted.
 6. A stamp asclaimed in claim 4, in which R2 is a carbon chain which has a lengthfrom the end group to X2 of 2-10 carbon atoms and preferably comprisesat least one perfluorinated carbon atom and is saturated.
 7. A stamp asclaimed in claim 6, in which R2 is branched at the free end, each branchcomprising at least one perfluorinated carbon atom.
 8. A stamp asclaimed in claim 4, in which n is
 0. 9. A stamp as claimed in any one ofthe preceding claims, in which the group Q is a sulphur bridge.
 10. Amethod of manufacturing a stamp for use in transferring a pattern innanoscale, which stamp has a monomolecular antisticking layer,characterised in that the surface of the stamp is provided withmolecular chains, which are covalently bound to the surface of the stampand which each comprise at least one fluorine-containing group and agroup Q, which comprises a bond which is weaker than the other bonds inthe molecular chain as well as the covalent bond that binds themolecular chain to the surface of the stamp, splitting of said bond inthe group Q creating a group Q1, which is attached to the part of themolecular chain being left on the surface of the stamp and which iscapable of reacting with a fluorine-containing compound to restore theantisticking layer.
 11. A method as claimed in claim 10, in which thesurface of the stamp is treated by being reacted with a first reagent,which has a first functional group, which is hydrolysable, and a secondfunctional group, thus binding the first functional group of the firstreagent to the surface of the stamp, subsequently treating the surfaceof the stamp with a second reagent, which has a first end, which iscapable of reacting with the second functional group of the firstreagent, and a second end, which comprises at least onefluorine-containing group, and binding the first end of the secondreagent to the second functional group of the first reagent, therebyforming the group Q.
 12. A method as claimed in claim 11, in which thefirst reagent is converted into gaseous phase before it is reacted withthe surface of the stamp.
 13. A method as claimed in claim 11 or 12, inwhich the treatment with the second reagent is carried out in liquidphase.
 14. A method of repairing a damaged monomolecular antistickinglayer on a stamp as claimed in claim 1, characterised in that the stampis treated with a repairing reagent, which has a coupling end, which iscapable of reacting with the group Q1, and a fluorine-containing grouplocated at the other end of the repairing reagent, that the coupling endof the repairing reagent is bound to the group Q1 which is attached tothe surface of the stamp, the group Q being formed anew.
 15. A method asclaimed in claim 14, in which the stamp is first treated for splittingsubstantially all groups Q.